The morphological and physiological responses of Pinus yunnanensis to different levels of shading after decapitation

Pinus yunnanensis is an endemic forest vegetation in Southwest China. Currently, most reforestation of P. yunnanensis is conducted using seedlings, which often results in significant variation among the progeny. In contrast, stable inheritance of characteristics from the parent tree can be ensured through clonal propagation. For the success of clonal propagation of P. yunnanensis, the nutrient content and the quality of the shoot branches play a crucial role. This study focuses on P. yunnanensis seedlings as the research subject, conducting decapitation treatments under 0 %, 25 %, 50 %, and 75 % shading conditions, while maintaining a seedling height of 10 cm. Measurements were taken for seedling height, plant diameter, root morphology, and nutrient content. The results indicated that shading advanced the rapid growth phase of decapitated P. yunnanensis seedlings while also extending the rapid growth period and the shoot branching peak. In addition, From the perspective of the effects of shading on belowground parts, light shading can promote lateral root growth and improve nutrient absorption efficiency. Moreover, shading treatment increased the nitrogen and phosphorus content, with nitrogen being the limiting element responding to shading. Additionally, shading altered the nutrient stoichiometric characteristics of the shoot branches. In conclusion, P. yunnanensis is a shade-tolerant species, and light shading is more favorable for increasing nutrient content in shoot branching, thereby promoting their growth and development.